Bilbo and the dwarves make use of the supplies and ponies the men of the town give them, and take two days to ride to Smaug’s Desolation, the area around the Mountain that Smaug has claimed for himself. They are not cheery as they ride, since they know that they are nearing the end of their journey, and it might be an unpleasant end.
The climactic scenes of The Hobbit are about to begin, and everyone, including the dwarves, Bilbo, and Tolkien himself, knows it.
The group reaches the remains of Dale, which is in ruins. Thorin and Balin note sadly that the Dale was green and beautiful before Smaug destroyed it. Bilbo sees smoke rising from the Mountain, and assumes that Smaug must still be there. Balin says that he’s probably right, but that Smaug could be gone for a time, with the underground halls still full of his smell.
Part of Smaug’s danger to the dwarves is that he’s unpredictable—surprisingly for such a large, visible animal. Thus, it’s not even clear that he’s really under the mountain.
The dwarves are afraid of what they’ll encounter in the mountain, and have little spirit for their quest. Bilbo, surprisingly, is eager to use the map to find the secret passageway. However, after many days of looking, they do not succeed in finding it. Autumn is almost over, and winter is about to begin: at this point in the quest, the entire group, even Bilbo, begins to despair. Bilbo looks to the West and thinks fondly of his home. The dwarves suggest that he try to enter the Kingdom under the Mountain through the Main Gate; Bilbo turns down this suggestion immediately, since he’d likely to run into Smaug, and the dwarves reluctantly accept his decision.
Though Bilbo was initially reluctant to go to the mountain, the sight of the map—he’s loved maps since long before he began the quest—reinvigorates his spirits. This, and the other conversations Bilbo has with the dwarves in this section, suggests that defeating Smaug is as much a practical problem as one of bravery—they have to figure out how to enter the mountain first.
Several days after they arrive at the Lonely Mountain, there is a new moon in the sky and the sun is setting. Bilbo sees a thrush knocking a snail against the rock, and this sight reminds him of the message Elrond read on the map: he realizes that he has found the secret entrance, and it is Durin’s Day, the dwarf New Year. This means that the group can open the passageway. As the sun sets that evening, a single red ray of light shines on the side of the mountain; a rock falls, illuminating a keyhole, just as Elrond predicted. Quickly, Thorin produces his key, turns it in the keyhole, and opens a door into the side of the Lonely Mountain.
Bilbo continues to prove himself valuable to the quest, but his heroism here is based on traits not always connected to heroism (but which Tolkien seems to indicate should be). He is observant, and has a better memory than the other dwarves—he remembers that Elrond told them that on Durin’s Day, the light of the sun would shine on the door to the secret passageway. The thrush proves a valuable ally to the dwarves, for reasons that Tolkien will make clear later on.